Bug#998062: Please change default dbus implementation to dbus-broker

[Luca Boccassi]

retitle -1 Allow using dbus-broker if the user installed it

On Fri, 2021-10-29 at 12:11 +0200, Michael Biebl wrote:
> Package: at-spi2-core
> Version: 2.42.0-1
> Severity: wishlist
> Tags: patch
> X-Debbugs-Cc: bluca at debian.org, smcv at debian.org
> 
> Hi,
> 
> I currently have dbus-broker installed and enabled:
> 
> michael at pluto:~$ apt-cache policy dbus-broker
> dbus-broker:
>   Installed: 29-2
>   Candidate: 29-2
>   Version table:
>  *** 29-2 500
>         500 http://ftp.debian.org/debian sid/main amd64 Packages
>         100 /var/lib/dpkg/status
> michael at pluto:~$ systemctl status dbus.service
> * dbus-broker.service - D-Bus System Message Bus
>      Loaded: loaded (/lib/systemd/system/dbus-broker.service; enabled; vendor preset: enabled)
>      Active: active (running) since Fri 2021-10-29 10:58:51 CEST; 13min ago
> TriggeredBy: * dbus.socket
>        Docs: man:dbus-broker-launch(1)
>    Main PID: 591 (dbus-broker-lau)
>       Tasks: 2 (limit: 19028)
>      Memory: 5.8M
>         CPU: 622ms
>      CGroup: /system.slice/dbus-broker.service
>              |-591 /usr/bin/dbus-broker-launch --scope system --audit
>              `-596 dbus-broker --log 4 --controller 9 --machine-id 567a68a5c2672114bcf5192d00000008 --max-bytes 536870912 --max-fds >
> 
> Oct 29 10:58:51 pluto systemd[1]: Starting D-Bus System Message Bus...
> Oct 29 10:58:51 pluto systemd[1]: Started D-Bus System Message Bus.
> Oct 29 10:58:51 pluto dbus-broker-launch[591]: AppArmor enabled, but not supported. Ignoring.
> Oct 29 10:58:51 pluto dbus-broker-lau[591]: Ready
> 
> 
> 
> Yet, I still see that at-spi2-core launches a dbus-daemon instance
> itself:
> 
> michael at pluto:~$ ps aux | grep dbus
> message+     591  0.0  0.0   9744  4232 ?        Ss   10:58   0:00 /usr/bin/dbus-broker-launch --scope system --audit
> message+     596  0.0  0.0   6988  4468 ?        S    10:58   0:00 dbus-broker --log 4 --controller 9 --machine-id 567a68a5c2672114bcf5192d00000008 --max-bytes 536870912 --max-fds 4096 --max-matches 131072 --audit
> michael     1643  0.0  0.0   9540  3804 ?        Ss   10:59   0:00 /usr/bin/dbus-broker-launch --scope user
> michael     1711  0.0  0.0   7080  4616 ?        S    10:59   0:00 dbus-broker --log 4 --controller 10 --machine-id 567a68a5c2672114bcf5192d00000008 --max-bytes 100000000000000 --max-fds 25000000000000 --max-matches 5000000000
> michael     2062  0.0  0.0   8024  4256 ?        S    10:59   0:00 /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3
> 
> 
> This can be fixed by building at-spi2-core with
> -Ddefault_bus=dbus-broker
> This way, bus/at-spi-bus-launcher.c will first try to use dbus-broker
> and if not available fall back to dbus-daemon.
> 
> I rebuilt the package with the attached patch and applied and
> successfully tested
> - dbus-broker installed: → dbus-broker is used
> - dbus-broker not installed → dbus-daemon is used
> 
> I've CCed Simon and Luca as maintainers of dbus and dbus-broker, in case
> they have some input on this matter.
> 
> 
> Regards,
> Michael

Nice find, and for reference the fallback is here:

https://sources.debian.org/src/at-spi2-core/2.42.0-1/bus/at-spi-bus-launcher.c/?hl=405#L489

So given the default implementation is dbus-daemon it should be indeed
safe to try first dbus-broker, and fallback to dbus-daemon if not
installed.

I have taken the liberty to retitle slightly, to ensure it's clear that
the request is not to force to change to dbus-broker, but simply to
allow it to be used if the user chose it for their system.

Thanks!

-- 
Kind regards,
Luca Boccassi
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